"If you've requested we not have your permission, we'll acquire the data, and add a note that we are not allowed to use it".
To be fair, it's the data needed for patient care and clinical records. It's required to perform the service. The opt out is to allow them to use it for other things not specifically required to perform the service. Also, IIRC, it took a special exemption in the DPA and GDPR to allow it function as an opt out rather than the more usually required opt in.